Fire hydrant check valves are known in the industry. Such valves are designed to prevent water waste and property damage caused inadvertently when a fire hydrant is struck accidentally by a moving motor vehicle and dislodges from the water supply pipe. For example, U.S. Pat. No. 9,890,866 discloses a hydrant shear valve for a hydrant coupled in fluid communication with a hydrant water supply pipe having a pipe flange. The valve includes a valve body having fastener receiving openings for mounting the valve in fluid communication between the hydrant and the water supply pipe, the valve body having a valve seat, and a two-piece valve member having two separate valve member portions each separately and independently pivotally mounted in the valve body to move independently between open positions and closed positions. The separate valve member portions are disposed overlapping one another axially aligned within the valve body in the open position and disposed in a co-planar configuration in engagement with the valve seat in the closed position. A pair of bias members are provided for maintaining releaseably the valve member portions in the open position and permitting at least one of the valve member portions to be moved toward the closed position under a force of fluid flowing from the supply pipe. A pair of oppositely disposed recesses are provided in the top portion of the valve body, the pair of bias members including separate L-shaped bias members having rods for engaging the valve body recesses and each having a foot fixed to one of the valve members. The bias member rods are held down by the hydrant in the valve body recesses when the two-piece valve member is disposed in the open position and permitted to move freely out of the recesses when the hydrant is at least partially dislodged from the valve body. At least one actuator is provided for freeing the bias members to permit the valve member portions to move independently toward the closed position under the force of water pressure when the hydrant is hit with sufficient impact.
U.S. Pat. No. 10,060,101 discloses a dual plate backflow and breakaway check valve designed to mount above grade. The dual plate check valve includes a barrel assembly having an upper portion, a lower portion and an annular groove. An upper dual valve includes an upper front plate and an upper back plate. A lower dual valve includes a lower front plate and a lower back plate. A lower valve keeper bar moves up from between a plurality of lower valve stay tabs upon breakage of the annular groove thereby allowing the lower front plate and the lower back plate to rotate about a lower valve pin and closing the lower dual valve upon a lower barrel bevel and simultaneously allowing the upper front plate and the upper back plate to rotate about an upper valve pin and closing upon an upper barrel bevel.
U.S. Patent Application Publication No. 20050224114 discloses a pipe coupling for use with a fire hydrant having automatic shut-off features in the event of breakage of the fire hydrant. The breakaway pipe coupling includes an extension join to a valve body with a flow passage way extending through the extension and valve body. A shut-off valve is moveably mounted to the extension and is bois for movement toward a valve seat located in the valve body. A wedge extends between the extension and the shut-off valve, wedging the shut-off valve in a open position away from the valve seat. Extension and valve are separably joined together in that the extension includes a frangible portion which severs upon application of an impact force to pipe coupling. This allows the wedge to become dislodged, with the shut-off valve being urged in a position towards the valve seat.